The HIV Preclinical Vaccine Development Master Agreement Program was initiated to enable the NIAID to provide resources to accelerate the development of promising vaccine approaches. Under this program, a series of vaccine studies have been initiated to evaluate candidate and prototype AIDS vaccines in nonhuman primates. These studies are designed to obtain more information about the efficacy and optimum presentation of candidate HIV vaccines that are in human Phase I clinical trials or proposed for such trials as well as prototype SIV vaccines of the same type as these HIV vaccines. Other vaccine studies will evaluate prototype HIV or SIV vaccines that offer novel presentation systems, may be capable of eliciting broadly cross-reactive immune responses, or have shown promising preliminary results. NIAID has initiated collaborative arrangements with researchers who have agreed to provide HIV and SIV vaccines for immunization of nonhuman primates. In all of the vaccine studies, the nonhuman primates will be challenged after immunization to determine if protection from infection or from disease can be obtained. The contractors in Category E of the Master Agreement Program, including the contractor listed above, will provide the laboratory support for these various vaccine studies. The laboratory support work is divided into two parts. Part A pertains to animals immunized with HIV vaccines and challenged with SHIV, and Part B assays pertain to animals immunized with SIV vaccines and challenged with SIV. In all cases assays will be performed such as ELISA and Western Blots to assess the humoral immune responses of immunized macaques. Virus isolations such as co-culture and limiting dilution will be performed to determine if virus infection has occurred after virus challenge. The Category E contractors will maintain a test results database for each study, and will transfer data electronically to the AIDS Vaccine Evaluation Group Statistical and Coordinating Center. In addition, the Category E contractors will provide facilities and equipment to conduct biosafety level 2 or 3 laboratory work.